Matrix switch utilizing magnetic structures as crosspoints



2 Sheets-Sheet 1 FIG. /B

E. E. SCHWENZFEGER (D00 "DI" l0 4 DIO svo MATRIX swITcH UTILIZING MAGNETIC STRUCTURES As cRossPoINTs Filed Nov. 4. 1958 FIG. /A

July 3o, .1963

SHO @im 93H2 RH2 .de

www/"0R BV E. E. SCHWENZFEGER @www /77 QM/t ATTOA/Ey July 30, 1963 E E, SCHWENZFEGER 3,099,752

MATRIX SWITCH UTILIZING MAGNETIC STRUCTURES AS CROSSPOINTS Filed Nov. 4. 1958 2 Sheets-Sheet 2 A 7' TOR/VE V United States Patent O 3,099,752 MATRIX SWITCH UTILIZING MAGNETIC STRUCTURES AS CROSSPOlNTS Edward E. Scliwenafeger, Bayside, NY., assgnor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Filed Nov. 4, 1953, Ser. No. 771,924 9 Claims. (Ci. 307-38) This invention relates to a matrix switch and more particularly to la matrix switch using magnetic elements as crosspoints.

The increasing use of data switching systems and other complex communication systems in which intelligence is transmitted from one point to 4another makes highly desirable the provision of improved switching arrangements for connecting `a selected one of `a plurality of conductors in a rst group to a selected one of la plurality of conducto-rs in a second group. At the present time, switching operations of this type :are often performed with the :aid of electromechanical devices such -as relays, Strowger type step-by-step switches or crossbar switches. Although these devices #are well suited for the purposes 'for which they were designed, ie., for use in relay switching systems, none of them are ideally suited for use with electronic switching systems for several reasons. First of all, the operate time of these devices is usually in the order of milliseconds while electronic switching systems can easily complete a switching function in la few microseconds. Secondly, the relatively large current requirements .of these devices makes them unsuitable for use with the low current components used in electronic systems such as, for example, transistors, magnetic cores, et cetera.

It is an object of the invention to provide an improved switching means for interconnecting `a selected conductor in a iirst group of conductors to ia selected conductor in a second group of conductors.

`lt is a further object of the invention to provide an improved switching means having a fast operate time and low current requirements -for interconnecting a selected conductor in a firstgroup of conductors to a selected conductor in ia second group of conductors.

In `accordance with the present invention, a plurality of magnetic elements are utilized as crosspoint elements in a matrix switch. Each clement has two signal windings and a clamping winding. The two signal windings ,are normally non-flux connected so that fa signal applied to one will not be induced in the other. However, when a current of sutlicient magnitude is caused to dow through the clamping winding, the tluX paths 4are `altered to link the two signal windings iiuxwise, thereby causing a signal applied to one to be induced in the other.

Each magnetic element is ladder shaped in that imauy be said to have three rungs and two side rails. The two end rungs each have a signal winding thereon while the clamping winding is on the middle rung. Each element also has two states, la .clamped yand an unclamped state.

A voltage applied to a signal winding produces a signal llux in its associated end rung. ln the normal or unclarnped state (no current flowing through the clamping winding) the path for this signal flux is completed through one side rail, the middle rung, the other side rail, and hack to the same yend rung. Thus, in this condition, the iiux induced =by a signal winding completes its return path through the middle rung and does not travel through the distant end rung to induce a voltage in the other signal winding. If, however, the clamping winding is energized to saturate the middle rung iluxwise, the signal flux induced in an end rung cannot ilow through the middle rung and therefore, will lne forced to complete its return path via the distant end rung, there-by inducing la voltage in the other signal winding.

ice

It may be seen that each magnetic element comprises a switch which either connects or Idisconnects the two signal windings from each other fluxwise. When the two are so connected, a signal applied to one will be induced in the other and conversely, when the two are disconnected, a signal applied to one signal winding will not he induced in the other. The clamping winding is the controlling element ,and the :absence or presence of saturation current therein determines whether the switch is to be opened or closed.

A plurality of the above-described magnetic elements are arranged in ta matrix configuration having rows and columns. The top rung signal win-dings common to a row are connected in series :as are the bottom rung signal windings com-mon to a column. Also, a plurality of control buses are provided, one -tfor each row and one for each column. Each magnetic element has one side of its clampi-ng winding connected to the control bus for its row while the other side of its clamping winding is connected to the control bus for its column.

An input signal .applied to the series circuit comprising the top rung signal windings lfor a certain row will cause a flux to be induced in the top rungs of the magnetic elements common to the row. However, if all elements in this row are lin their unclamped state, none of the signal flux will travel through the bottom rungs and therefore, no voltage will be induced in any of the :bottom rung signal windings of this row. v

When it is desired to close a particular crosspoint, appropriate potentials are applied to the horizontal and .vertical control buses common to this crosspoint, thereby energizing its clamping winding. Once clamping current is owing through this particular crosspoint, -the application of a signal to the series circuit comprising the top rung signal windings of the row containing this crosspoint will cause the induced signal ilux to travel `from the top rung of this crosspoint, through the lbottom rung and hack around to the top rung, thereby inducing a similar signal in the bottom rung signal winding. The signal induced in the bottom rung winding appears on the signal lead lfor the column :associated with this crosspoi-nt.

Since the top rung signal windings for each row 'are connected in series, the lluX induced in the top rung of the closed crosspoint will likewise be induced in the top rung of each open crosspoint in the same row. However, these other :crosspoints Iare in an unclamped condition at this time, and therefore, this flux will complete Ia return path `for itself through the middle run-gs and will induce no output potential in the `bottom rung windings.

It may be seen .that ,the present invention comprises the electronic equivalent of the well known .crossbar switch in that it provides for the interconnection of any one of a plurality of wires in :a tir-st group with [any one of :a plurality of wires in 1a second group. Further, the elements used to accomplish this have ran operate time and power requirements that are fully compatible with the components comprising the present day electronic switching systems.

A feature of the invention is the use of a magnetic element having selectively controllable flux paths las a crosspioint of a matrix switch.

A further `feature of the invention is ithe Iprovision of a plurality of magnetic elements each having a pair of sign-al windings in combination with means whereby upon the application of a signal to one winding :of each element simultaneously means are effective to provide a signal output from the other winding of only one of said elements.

-A further feature tof the invention is .the provision of a plurality of magnetic elements each having a first and a second signal winding [and 1a clamping winding together with means effective when a signal input is applied simultaneously to one winding of each element ior controlling the clamping winding of all elements to determine which element shall have its signal windings linked iluxwise whereby an output signal appears on the :other signal winding of only this element.

A further feature of the invention is the provision of a plurality of magnetic elements arranged in a matrix contigui-ation :and each having a plurality of `signal windings whereby upon the application :of an input signal to all the elements in a given row, an output signal appears on the other signal winding of only a selected one of the element-s in said row.

A further feature lof the invention is the provision of a plurality of magnetic crosspoints arranged into columns and rows and each having a plurality of signal windings with the rst signal winding of lall crosspomts being connected in series for each now and with the second signal winding common to a column :being connected in series together with means whereby upon the application of a signal input to one :of the series circuits common to a row an output signal is received by only one of the series circuits common to a column.

A further `feature `of the :invention is the provision of a three-dimensional matrix switch having .a plurality aof magnetic elements Kas crosspoints in combination with means whereby the elements may be `selectively controlled to effect .the interconnection of a plurality of conductors in a inst group with a plurality of conductors :in a second group.

These and other objects and features of the invention will be more readily understood when read in connection with the following detailed description and drawings in which:

FIGS. 1A, 1B and 1C disclose the magnetic structures used as crosspoint elements in the matrix Switch oomprising the present invention;

FIG. 2 )discloses a circuit utilizing a plurality of these magnetic elements and comprising a matrix switch; and

FIG. 3 discloses a circuit utilizing a plunality of these magnetic elements as a three-dimensional matrix switch.

Inasmuch as the matrix switch of the present invention utilizes magnetic elements which are relatively new in the ar-t, the rst portion of this description comprises a brief Iand simplified description of characteristics of these elements. From the drawings it may be seen that these elements are ladder shaped in that they have a top, a middie and a bottom rung together with two side rails. The side rails and all of the -rungs are equal in minimum cro-sss'ectional area so that all flux paths within the device have the same flux carrying capacity. Also, ias is genenally true in magnetic structures, ux induced in these elements always seeks to complete a return path for itself by the shortest available flux path.

Referring to FIG. 1A, let it be assumed that a current is caused to ilow through the top rung winding 4 to orient the ux in the top rung clockwise as shown by the arrows. Experiments have revealed that the flux induced in the top r-ung by current in winding y4- will complete a path for itself through the upper half of the right-hand side rail, through the middle rung, through lthe upper half of the leftahand side rail and back to the top rung. Inasmuch as this flux always utilizes the closest available return path, and, due to the -fact that all rungs are equal in cross-sectional area, little or none of the flux induced in the top rung by the current through winding 4 will flow through the bottom rung. The unmagnetized state of that part of the device comprising the lower rung torgether with the lower portion of the two side rails is represented by the dotted arrows which complete :a closed path for themselves.

In summary, insoiar as concerns the embodiment of FIG. 1A, 4it may be seen that signals applied to winding 4 will not be induced in winding S since the two windings are not flux connected.

Let us now take the embodiment :of FIG. 1A and to it :add a clamping winding 6 on the middle rung. Let it be :assumed that no signals are applied to `either of windings 4- or 5 :and that a current is caused to ilow through clamping winding 6 so as to saturate the middle rung in the direction shown by the arrows. The Itop and bottom rungs :are of equal dista-nce from the middle rung and therefore, the fiux .induced in the middle rung finds two equally accessible return paths for itself. As a result, half of this flux is completed via the top rung while the other half is completed via the bottom rung. Thus, while the clamping current is applied, the top rung is half saturated, the middle rung is fully saturated, and the bottom rung is half saturated.

The embodiment of FIG. `1C is similar to .that of FIG. 1B except that a signal is applied to winding 4 while eiamping current is applied to winding 5. The iiux developed by the clamping current continues to flow equally through the top and bottom rungs. This is shown in FIG. 1C .as it was in FIG. 1B with the solid clockwise arrows around the upper aperture representing the half of the clamping ilux which ilows through the top rung while the solid counterclockwise arrows around the lower aperture represent the ux tlowing through the bottom rung. Let it be assumed that the signal now 'applied to winding 4 induces a signal ux in the unsaturated portion of the top rung in the direction indicated by the dotted arrows. This flux travels down the left side rail to the middle rung which is currently unavailable as a return path since it is held saturated by the clamping current. Therefore, the signal flux continues its downward travel until it meets the lower rung. A return path is available through this rung since it is only half saturated at this time by the clamping current. The signal flux from winding 4 ilows through this rung and up the right side rail, and returns to the top rung. The signal flux owing thnough the bottom rung is identical to that induced in .the top rung and therefore, a signal voltage is induced in the bottom rung winding 7 which is identical to that applied to the winding 4.

if the signal applied to winding 4 reverses in polarity, the dotted arrows representing tl .e signal ilux also reverse in direction. The ilux induced by the reversed signal polarity is also unable to complete a return path through the middle rung and, for the same reason, completes its return path through the bottom rung and induces a similar signal -in winding 5.

From the above it may be seen that any signal applied to winding 4 during the time the middle rung is held saturated produces a ilux change in the top rung which, due to the unavailability oi the middle rung as a tlux path, produces a corresponding tlux change in the lower rung. Since the linx changes in the top and bottom rungs are equal, the same signal applied to winding d is induced in winding 5 of the bottom rung.

ln summary, it may be seen that the device ofgFIG. 1C acts as a switch to connect or disconnect windings 4 and 5 iluxwise with the current through the clamping winding being the determining factor as to whether the two signal windings are to be connected or disconnected.

The preceding discussion is intended only as a brief and simplified description of the characteristics of the magnetic structures utilized as crosspoint elements in the present invention. Reference is made to the T. H. Crowley- U. F. Gianola U.S. Patent No. 2,963,591, issued December 6, 1960, Ifor a more sophisticated treatment of this subject.

FIG. Q. discloses the circuit of a matrix switch utilizing the magnetic structure of FIG. 1C as crosspoint elements. This switch has thirty crosspoints contained in three rows and ten columns. Crosspoints 09 through @9 comprise the top row of the switch, crosspoints l0 through 19 the middle row, and crosspoints 2d through 29 the bottom row.

The top rung windings in each row are connected in series between one of conductors H0, H1 or H2 and ground. For example, the top rung windings of row 0, `crosspoints 00 through 09, are connected in series between conductor H0 and ground. The bottom rung windings common to a column are also connected in series between one of conductors V0 through V9 and ground. Thus, the bottom rung windings of column 0 are connected in series between ground and conductor V0.

A plurality of control conductors are provided, one for each row and one for each column. The control conductors associated with the rows are designated CH()` through CH2 while the control conductors associated with the columns are designated CVO through CV9. The clamping winding of each crosspoint is connected in series with a diode between the control conductor for its row and the control conductor for its column. For example, the clamping winding of crosspoint 00 is connected from control conductor CHO in series with diode Dtltl to control conductor CVO.

Make contacts SH() -through SH2 respectively, when closed, connect a negative potential to conductors CHG through CH2 respectively, through resistors RHG through RHZ, respectively. Similarly, make contacts SVtl through SV9 respectively, when closed, connect conductors CV() through CV9 respectively, in series with resistors RVi) through RV9 respectively, to a source of positive potential. Resistors Ittl-(l through 10U-9 provide a path to ground for each of conductors CVtl through CV9.

In order -to describe the operation of the switch, let it first be assumed that a signal is applied to horizontal conductor Htl at the time when all crosspoints are in an unc-lamped condition. The signal applied to conductor H0 effects a current flow from conductor H0 to ground through the series circuit comprising the top rung windings of crosspoints 00 through 09. This current induces a signal iflux in the top rung of each of these crosspoints. Since `it has been assumed that all crosspoints are in an unclamped condition, the signal -flux induced in each top rung at this time completes a return path for itself through the middle rung. This leaves the ux in the bottom rung of each of crosspoints 00 through 69 in an unchanged condition so that no signal is induced in their bottom rung windings.

Similarly, if a signal were applied to conductor V0 instead of H0, the induced signal iiux in the lower rungs of the crosspoints in column (t` would complete a return path for itself through the middle rung and thereby leave the -ilux in the top rung `in an unchanged condition so that no signal would be induced in any top rung winding in column 0. The same is tr-ue with respect to the crosspoints in all of the other rows and columns so that the application of a signal to any of conductors HI, H2, VI through V9 will not induce a corresponding signal in the opposite end rung winding of any crosspoint since all crosspoints have been assumed to be in an unclamped position.

Let it now be assumed that it is desired to etfect a closure of crosspoint 1-I in order to connect conductors HI and V1 signalwise. Make contacts SHI and SVI are closed `in order to effect this interconnection. The closure of these contacts completes a path frorn negative potential through contacts SHI, resistor RHI, the clamping winding of crosspoint 1.1, diode D11, resistor RVI, contacts SVI, to a source of positive potential. The diodes yassociated with the crosspoints are of the breakdown type, such as, for example, Zener diodes or cold cathode gas tubes, whereby no conduction takes place until a suicient-ly large breakdown voltage is applied across the diode, after which time a much 'lower voltage will sustain conduction therethrough. If Zener diodes are used, reverse breakdown Iand conduction potentials should be applied as shown on FIG. 2. -If gas tube diodes are used, the polarity of the breakdown and conduction potential is immaterial since such tubes may be ionized by the application of either a forward or a reverse voltage. The closure of contacts SHI and SVI places a sufficiently lange potential across diode DLI to effect its breakdown. Contacts SVI are opened subsequent to the breakdown of diode DIiI and the path yfor the sustaining current then includes resistor Imi-I rather than resistor RVI and contacts SVI. The current flowing from the negative potential on closed contacts SHI through the above-described path to ground on resistor 10U-1 is sufficient to maintain saturation in the middle rung of crosspoint II.

A signal `applied to conductor HI at this time induces a signal flux in the top rung of each of crosspoints 10 through 19. This flux effects no corresponding signal flux in the lower rungs of any of crosspoints 10 and 12 through I9 for the reasons already described since all of them are in ian unclarnped position. However, the signal flux induced in the top rung of crosspoint 11 nds the middle rung unavailable Ias a return path due to its saturated condition and, therefore, completes a return path for itself through the bottom rung. The ux change in the bottom rung, due to the applied signal on conductor HI, induces a corresponding signal in the bottom rung winding of crosspoint I1. This induced signal is applied through the bottom rung windings of the other crosspoints of column 1 to conductor VI'. Similarly, any signals applied to conductor VI would, by the same considerations, cause :an output signal to be applied only to the top rung winding of crosspoint I1 and only to` conductor HI. The clamping current is maintained in crosspoint II for las long as it is desired to maintain communication between conductors HI and VI.

At the same time conductors HI and VI are interconnected, additional interconnections can be made between conductors H0, H2 and yany of the remaining conductors V0, and V2 through V9. For example, switches SH2 and SV9 could be closed to energize the clamping winding of crosspoint 29, thereby interconnecting conductors H2 and V9 signalwise.

The above operation of switches SH2 :and SV9 only effects a closure of crosspoint 29'. Crosspoint 19 does not close at this time even thou-gh switch SHI, which was previously operated, remains operated while switch SV9 is operated. Crosspoint I9 is not closed due to lshe yfact that resistors RH@ through RH2 comprise lockout circuits which permit only a single crosspoint per row to be closed at any given instant of time.

These lockout circuits work in -the (following manner. Referring to conductor CHI for example, the full negative supply potential is applied to it immediately after the closure of switch SHI and prior to the breakdown of diode DII. However, after diode D11 breaks down, the flow of the resulting clamping current produces an IR drop across resistor RHI which raises the potential on conductor CHI in the positive -fdirection sufficiently so that the closure of any further column switches cannot effect the breakdown of any additional diodes inrow 1. Thus, the closure of switches SH2 and CV9, after crosspoint II has been closed, closes lcrosspoint 29 but does not close crosspoint 19 since the potential across diode D19 is insufficient to break it down.

Contacts SHI are opened when it is desired to open crosspoints I1 -to `disconnect conductors HI and V1 signalwise. The opening of contacts SHI removes the clamping current `from crosspoint I1 so that any subsequent signals applied to conductor HI will not appear on conductor VI, or vice versa, since the signal flux produced thereby will now complete a return path for itself via the middle rung.

In summary, it may be seen that the use of the magnetic elements shown herein as crosspoints in a matrix switch provides a new and novel means for selectively interconnecting any one of a plurality of conductors in a first group with any selected one of -a plurality of conductors in a second group. Further, the circuit used to accomplish this function has an operate time and power requirements that are fully compatible with the component elements of present day electronic switching systems.

Contacts SHO through SH2 and SV() through SV9 have been shown as conventional contacts in order to facilitate an understanding of the invention. However, when incorporating the principles of the present invention into an electronic switching system, the function of these contacts could advantageously be performed by some sort of an electronic switch, such as, for example, a gas tube, a vacuum tube or a transistor.

A plurality of the embodiments of FIG. 2 could be arranged to form a three-dimensional matrix switch in the event it should be desired to connect a selected subgroup of yconductors ina irst group to a selected subgroup of conductors in a second group. ln this case, all conductors in a subgroup would have their clamping windings connected in parallel. Thus, if each of conductors Htl through H2 and V0 through V9 represented twelve wires, the resultant switch would have twelve layers of FIG. 2 with the crosspoints of all twelve wires represented by conductor H0, for example, having their clamping windings paralleled whereby the closure of contacts SHt) and SVO would interconnect the twelve wires H to the twelve wires V0.

FIG. 3 discloses a switch of this type having two rows, three columns and two levels. Crosspoints tdLl, GlLi, and 02U. comprise row t) of level 3l while crosspoints OL, 01M), and 02U) comprise row (l of level t). Similarly, crosspoints L1, llLl, and iZLl comprise row l of level 1 while crosspoints 10U), 11L0, and 12D!) comprise row 1 of level 0. The crosspoints of row 0, level 1 have conductor HOLl as their signal input while the crosspoints in row 0, level (t have conductor HQLG as their signal input. Similarly, conductors HllLl and HIL() comprise the signal input conductors of levels l and tl, respectively of row 1. The output conductors for column (D are designated VtlLl for level 1 and VELG for level 0. The output conductors for the other columns are desig- -nated in a corresponding manner.

Control conductor CHG is common to the crosspoints in both levels 0 and l of row 0 while control conductor CHI is common to the crosspoints in levels 0 and 1 of row 1. Similarly, conductors CVI, CV, and CVZ are common to the crosspoints in both levels of columns 0, 1, `and 2, respectively.

The clamping winding of each crosspoint is connected in series with a `diode between the control conductor common to its row land the control lconductor common to its column. example, followed by the release of contacts SV@ effect a clamping current through both of crosspoints 00L() and 00L1 -thereby ylinking the two signal windings of both of these crosspoints iluxwise whereupon conductors HGL@ and HOL1, respectively, may communicate with conductors VGL() and VOL1, respectively. Other crosspoints are closed in a similar manner.

It is to be understood that the above-described arrangements are but illustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the invention. For example, the crosspoint elements utilized herein may be of material having a substantially rectangular hysteresis loop. This material would normally be utilized only when it is desired to take advantage of its memory capabilities. When such material is used in the circuit of FIG. 2, it would operate in the following manner. Switches SHI and SVI would be operated momentarily in order to effect a breakdown of diode D11 and thereby orient the flux in the middle rung of crosspoint 1l in a given direction. The flux will remain oriented in this direction .upon the release of these two switches until altered 4by a subsequently applied iluX.

The closure of contacts SH@ and SVG, for i At this time, only the middle rung of crosspoint 11 has its ilux oriented in the :direction of the previously applied lclamping current. If a pulse is now applied to conductor Hl, a signal ilux is induced in the top rung of each crosspoint in row 1. If the pulse applied to conductor H1 is of the proper polarity, only the signal flux in crosspoint l1 will travel through the bottom rung induce a corresponding signal in the wi-nding associated therewith since the ux induced in the other crosspoints of row 1 will complete a return path for itself through their associated middle rungs.

It the crosspoints of FIG. 2 are of material having remanent magnetic properties and, if the memory capabilities of the resulting embodiment are to be utilized, means must be provided for selectively reorienting the ux in each crosspoint to its original condition. This means may advantageously comprise a reset winding encircling one of the side rails of each crosspoint with the reset windings for all crosspoints in a row being connected in series as are lthe top rung signal windings. In this manner, the application of a reset pulse to the reset circuit for a row resets all crosspoints Within the row. Suitable reset circuits iare shown in the aforementioned T. H. Crowley et al patent.

What is claimed is:

1. A martix switch having a plurality of crosspoints arranged into columns and rows, each of said crosspoints comprising a magnetic element having a lirst and a second signal winding which are normally not ux connected, a clamping winding on each crosspoint effective when current `ilows therethrough to link the two signal windings of its crosspoint uxwise, means for connecting the first signal windings of all crosspoints common to a row in series between ground and a signal lead individual to each row, means for connecting the second signal windings of all crosspoints common to a column in series between ground and a signal lead individual to each column, means `for effecting a current in only the clamping winding of a selected crosspoint whereby the signal lead for the row in which said selected crosspoint is located is connected signalwise with the sign-al lead of the column in which said selected crosspoint is located.

2. A matrix switch having a plurality of crosspoints arranged into columns and rows, each crosspoint comprising a multiapertured magnetic structure having a primary 'and secondary ux leg which are normally non-ilux connected and a bypass iluX leg which is normally flux connected to said primary uX leg, said magnetic structure also being dimensioned whereby all ilux paths therewith have substantially the same ux capacity, a lirst signal winding on said primary leg, a clamping winding on said 'bypass leg, a second signal winding on said secondary leg, said clamping winding being effective when current llows therethrough to link the two signal windings of its crosspoint fluxwise, a tirst group of signal conductors e-ach of which is individually associated with one of said rows, a second group of signal conductors each of which is individually associated with one of said columns, means for connecting the rst signal windings of the crosspoints common to each row Ibetween a common ground .and the signal conductor individu-al to each row, means yfor connecting the second signal windings of the crosspoints common to each column between a common ground and a signal conductor individual to each column, and means for etfecting a current through only the clamping winding of a selected crosspoint whereby only the conductors common to said selected crosspoint are interconnected signalwise.

3. A matrix switch having a plurality of crosspoints arranged into columns and rows, each crosspoint comprising a multiapertured magnetic structure having a primary and secondary flux leg which are normally non-linx connected and a bypass flux leg which is normally ux connected to said primary flux leg, said magnetic structure also being dimensioned whereby all flux paths therewithin have substantially the same linx capacity, a first signal winding on said primary leg, a clamping winding on said bypass leg, a second signal Winding on said secondary leg, said clampin-g winding being effective when current flows therethrough to link Ithe two signal windings of its crosspoint fiuxwise, a -rst group of signal conductors each of which is individually associated with one of said rows, a second group of -signal conductors each of which is individually associated with one of said columns, means for connecting the first signal windings of the crosspoints common to each row between a common ground and the signal conductor individual to each row, means for connecting the second signal windings of the crosspoints common to each column between a common ground and a si-gnal conductor individual to each column, a first group of conrtol conductors each of which is individually associated with lone-s of said rows, a second group of control conductors each of which is individually associated with one of said columns, means for interconnecting the clamping winding of each crosspoint between the control conductor for its column and the control conductor for its row, and means for applying a potential `difference between a selected control conductor in said first group and a selected control conductor in said second group to effect a current Ithrough only Ithe clamping winding Iof the crosspoint common to said selected conductors whereby only the signal conductors common to said last-named crosspoint are connected signalwise. A

4. A matrix switch having a plural-ity of crosspoints arranged into columns and rows, each crosspoint comprising 1a multiapertured magnetic structure having a primary vand secondary flux leg which are normally nonflux connected and a bypass iiux leg which is normally flux connected to said primary fiux leg, said magnetic structure also being dimensioned whereby all flux paths therewithin have substantially the same fiuX capacity, a iirst signal winding on said primary leg, a clamping winding on said bypass leg, a second signal winding on said secondary leg, said clamping winding being effective when current flows therethrough to link the two signal windings of Iits crosspoint signalwise, a first group of control conductors each of which is individually associated with one of said rows, a second group of control conductors each of which is individually associated with one of said columns, means for interconnecting the clamping winding of each crosspoint between the control conductor for its column and fthe control conductor for its row, means for applying a potential dif-ference between a selected control conductor in said first group and 'a selected control conductor in said second group to effect a current through only the clamping winding of the crosspoint common to said selected conductors whereby only its signal windings are interconnected signalwise.

5. A three-dimensional matrix switch having a plurality of crosspoints divided into levels with each level having columns and rows, each of said crosspoints comprising a magnetic element having a first and a second signal Iwinding which are normally non-flux connected, a clamping winding on each crosspoint effective when current flows therethrough to link the two signal Windings of its crosspoint iiuxwise, `a first gro-up of control conductors each of which is individually associated with a different row in one of said levels and each of which is common to the corresponding row in each level, a second group of control conductors each of which is individually associated with a different column in one of said levels and each yof which is common to the corresponding column in each level, means for interconnecting the clamping winding of each crosspoint between the control co-nductors common to its row and column, and means for applying a potential difference between a selected control conductor in said first group and a selected control conductor in said second grou-p to eiiect a current in only the clamping windings of all crosspoints common to said selected conductors Ithereby linking fluxwise .the vtwo signal windings on only each of said lastnamed crosspoints.

6. A three-dimensional matrix switch having a plurality of crosspoints divided into levels with each level having columns and rows, each crosspoint comprising a multiapertured magnetic structure having a primary and secondary flux leg which are normally non-flux connected and a bypass flux leg which is normally iiux connected to said primary flux leg, said magnetic structure also being dimensioned whereby all flux paths within said structure have substantially the same flux capacity, a first signal winding on said primary leg, a clamping winding on said bypass leg, a second signal winding on said secondary leg, said clam-ping winding being effective when current flows therethrough to link Ithe two signal windings of its crosspoint signalwise, a first group of control conductors each of which is individually associated with a diiierent row in one of said levels and each of which is common `to the corresponding row in each level, a second group of control conductors each of which is individually associated with a different column in one of said levels and each of which is com-mon to the corresponding column in each level, 'means for interconnecting the clamping winding of each crosspoint between the control conductors common to its row and column, and means for applying a potential difference between a selected control conductor in said first group and a selected control conductor in said second group to effect a current in only the clamp-ing windings of the crosspoints common to both of said selected control conductors thereby linking fluxwise the two signal windings on only each of said lastnamed crosspoints.

7. A matrix switch having a plurality of crosspoints arranged into columns and rows, each crosspoint comprising a mnltiapertured magnetic structure having a first and second signal winding which are normally non-flux connected, each of said stnuctures also having a clamping winding which is effective when current flows therethrough to link the two signal windings of its crosspoint fluxwise, a first group of signal conductors each of which is individually associated with one of said rows, a second gro-up of lsignal conductors each of which is individually associated with one of said columns, means for connecting the first signal windings of the crosspoints common to each row between a common ground and the signal oonductor individual to each row, means for connecting the second signal windings of the crosspoints common to each colnmn between a common ground and a signal conduclt-or individual -to each column, a first Vgroup of control conductors each of which is individually associated with one of said rows, a second group of control conductors each of which is individually associated with one of said columns, means for interconnecting the clamping winding of each crosspoint between the control conductor for its column and the control conductor for its row, means for applying a potential difference between a selected control conductor in said iirst grou i and a selected control conductor in said second group `to effect a current through only the clamping winding of the crosspoint common to said selected control conductors whereby only the signal conductors common to said last-named crosspoint are interconnected signalwise.

8.V A matrix switch having a plurality of crosspoints arranged into columns and nows, each crosspoint comprising a multiapertured magnetic element having a first and a second signal winding which lare normally nonconnected signalwise, a iirst group of signal conductors each of which is individually associated with one of said rows, a second group of signal conductors each of which is individually lassocia-ted with one of said columns, means for yconnecting the first signal windings of the elements common to each row between a common ground and the signal conductor individual to each row, means for connecting the second signal windings of the elements common to each column between a common ground and the signal conductor individual to each column, a clamping winding on each of said elements effective when current flows therethrough `to link the signal windings of its element signalwise, and means for electing a current in the clamping winding of only a selected one of said elements whereby .only the conductor in said first `gnoup and the conductor in said second :group associated with said selected element are interconnected si'gnalwise as long as said clamping current persists.

9. A matrix switch having la plural-ity of :crosspoints arranged into columns and rows, each of said crosspoints comprising `a magnetic element having Ia first and second signal winding which are normally non-ux connected, a clamping winding on each crosspoint effective when current flows therethrough to `link the two signal windings of its crosspoint fluxwise, `a rst group of control conductors each of which is individually associated with one of said rows, .a second 'group of control conductors each of which is individually associated with one of said columns, la plurality of diodes each of which interconnects the clamping winding of a `crosspoint lbetween t'ne control conductor `or its 4row and the control conductor for its column, means -for connecting uxwise the windings of a selective element by applying a potential difference `between the control `conductor `for the row containing said selected element and the control conductor for the column containing said selected element .thereby effecting a current in the clamping Winding of said selected element.

References Cited in the tile of this patent UNITED STATES PATENTS 2,218,711 Hubbard Oct. 22, 194() 2,740,949I Couniharn Apr. 3, 1956 2,753,510 Smith July 23, 1956 2,814,031 Davis Nov. 19, 1956 2,840,801 Beter `Tune 24, 1958 2,869,112 Hunter Jan. 13, 1959 2,881,414 Haynes Apr. 7, 1959 2,898,581 Post Aug. 4, 1959 2,923,923 Raker Feb. 2, 1960 2,926,342 Rogers Feb. 23, 1960 2,931,017 Bonn Mar. 29, 1960 

1. A MARTIX SWITCH HAVING A PLURALITY OF CROSSPOINTS ARRANGED INTO COLUMNS AND ROWS, EACH OF SAID CROSSPOINTS COMPRISING A MAGNETIC ELEMENT HAVING A FIRST AND A SECOND SIGNAL WINDING WHICH ARE NORMALLY NOT FLUX CONNECTED, A CLAMPING WINDING ON EACH CROSSPOINT EFFECTIVE WHEN CURRENT FLOWS THERETHROUGH TO LINK THE TWO SIGNAL WINDINGS OF ITS CROSSPOINT FLUXWISE, MEANS FOR CONNECTING THE FIRST SIGNAL WINDINGS OF ALL CROSSPOINTS COMMON TO A ROW IN SERIES BETWEEN GROUND AND A SIGNAL LEAD INDIVIDUAL 